The objective of this trial is to assess the efficacy (structural changes in joint space width as measured by semi-flexed x-ray, and clinical changes as measured by either a Clinical Response [Non-progressor] rate [which includes measures of WOMAC pain, WOMAC function and analgesic usage] or the WOMAC pain subscale alone) and safety of BAY 12-9566 in relation to placebo, in patients with osteoarthritis (OA) of the knee, over 3 years.